Basement membrane assembly, stability and activities observed through a developmental lens.

Basement membranes are cell surface associated extracellular matrices containing laminins, type IV collagens, nidogens, perlecan, agrin, and other macromolecules. Biochemical and ultrastructural studies have suggested that basement membrane assembly and integrity is provided through multiple component interactions consisting of self-polymerizations, inter-component binding, and cell surface adhesions. Mutagenesis in vertebrate embryos and embryoid bodies have led to revisions of this model, providing evidence that laminins are essential for the formation of an initial polymeric scaffold of cell-attached matrix which matures in stability, ligand diversity, and functional complexity as additional matrix components are integrated into the scaffold. These studies also demonstrate that basement membrane components differentially promote cell polarization, organize and compartmentalize developing tissues, and maintain adult tissue function.